Tripping device for the blanket cylinders in offset printing machines



July 22, 1958 w. KOCH 2,844,096

TRIPPING DEVICE FOR THE BLANKET CYLINDERS IN OFFSET PRINTING MACHINES Filed March 21, 1955 2 Sheets-Sheet 1 fi omvir July 22, 1958 w. KOCH 2,844,096

TRIPPING DEVICE FOR THE BLANKET CYLINDERS IN OFFSET PRINTING MACHINES Filed March 21, 1955 2 Sheets-Sheet 2 United States Patent i TRIPPIN G DEVICE FOR THE BLANKET CYLIN- DERS IN OFFSET PRINTING MACHINES Werner Koch, Olfenbac h am Main, Germany, assignor to Faber & Schleicher Aktiengesellschaft, Otienbach am Main, Germany, a German body corporate Application March 21, 1955, Serial No. 495,732

' Claims priority, application Germany April 3, 1954 5 Claims. (Cl. 101-218) In connection with three-cylinder offset printing machines tripping devices are known in which the trunnions of the blanket or rubber cylinders are journaled in eccentric bushings. By the turning of these bushings the blanket cylinder is tripped first to the plate cylinder and consecutively to the impression cylinder. Tripping-01f takes place in the reversed way. The turning gear for these known devices is of such character that the two stages of tripping-on or on. are run through within one single rotation of the cylinder without the possibility of stopping them until they are completed. This is to say that once the action of tripping in either direction has been initiated it must be carried through to the end.

"A disadvantage of this arrangement is to be seen in that at the beginning of the printing operation the ink covering on the first batch of prints is not as good as it is on the subsequent prints. The reason for this behaviour in the indirect printing methods may be found in a kind of splitting up of the color, which does not allow the whole of the freshly applied coat to soak evenly into the blanket. In fact, merelya part of iris first taken up by the blanket and transferred to the paper to be printed, and it is not until after a number of prints have been made that the rubber blanket has become sufiiciently saturated with the color and that, after a certain state of compensation has been attained, the sheets will be evenlycovered with color, so that only then good prints can be obtained.

The invention avoids the aforesaid discrepancies by the provision of a tripping device in which an even coat of ink or color is ensured right in the beginning of the actual printing operation so that already the first sheets will be printed in the same richness of color as the sheets which are produced during the continued run of the machine.

The invention also provides means, in a tripping device of the aforesaid kind, which permits the tripping either of both cylinders, namely the plate cylinder and the impression cylinder, in succession as heretofore, or of tripping the plate cylinder without being immediately, if at all, followed by the tripping of the impression cylinder. By these means it is possible to continue inking the blanket by the plate cylinder during as many revolutions of the cylinder as desired before tripping the blanket cylinder to the impression cylinder, and prior to the first sheet being printed. In this way it is ensured that already the first sheet when printed appears already in the same richness of color which up to now could only be obtained in the running-on of the machine with the blanket properly saturated.

The invention further provides that the blanket cylinder may be tripped-off any time after the first tripping-on stage, that is before it has been tripped to the impression cylinder, which is of particular advantage for the examination of the image on the blanket cylinder because in this stage the ink covering thereon appears in its Patented July 22, 1958 2 full intensity and clearness still undisturbed by the printing of even a single sheet.

The invention still further provides means for the control of the tripping of the cylinders, which shall be simple in construction and effective in use, and which may be put into reliable operation either by hand or by a suitable gear from the machine.

In order to obtain the aforesaid purposes and advantages the invention substantially consists in a tripping device of the aforesaid kind in which a control member is provided by which the means for turning the conventional eccentric bushing of the blanket cylinder can be set to rest after the plate cylinder has been tripped on, so that the subsequent stage, namely the tripping of the impression cylinder, need not take place.

From the foregoing it will be seen that the invention can claimv several advantages over the tripping devices which were used up to the present. A further and very important advantage is the great simplicity of construction owing to the fact that a number of hitherto used parts can be used which, in conjunction with certain novel parts and features, will bring about the desired effects of the invention.

A particularly simple and yet very eflicient construction of a device in accordance with the invention comprises a conventional link and pawl arrangement as a turning gear, by means of which a turning movement can be imparted to the eccentric bushing of'the blanket cylinder and in which a unidirectly rotated cam is used to impart oscillatory movement to an abutment carrier which causes the on and off tripping of the blanket cylinder in the tripping it first to the said plate cylinder and consecutiv'ely to the impression cylinder. A further abutment is provided on the abutment carrier which, when brought into contact with the said pawl, eflects the tripping-0E of the device. A turning member, such as a manually or mechanically operated cam for instance, is provided by means of which the tripping pawl may be caused to cooperate with either of the two tripping abutments as required.

Evidently the arrangement of the device just described may be reversed in that the pawl carrier receives the oscillatory movement while the abutment carrier transmits it to the eccentric bushing of the blanket cylinder.

A modified example of .the invention, in which also use is made of a pawl for the tripping movement of the eccentric bushing of the blanket cylinder, provides that by correspondingly shaping the control cam a short rest may be caused in the rocking movement of the abutment carrier between the two tripping-on stages.

As an alternative a slight return movement may be imparted to the abutment carrier after the plate cylinder has been tripped, during which return movement the pawl, is disengaged again from the respective abutment, so that the blanket cylinder will be tripped to the plate cylinder only, but not to the impression cylinder unless the pawl is being reset. In this case it would be possible to provide a spring-controlled switch or the like which,

into the track of a roller on the controlpawl, so that during the standstill, or the return movement of the abutment carrier respectively, the pawl becomes released after the first tripping stage as by means of a spring for example. I

The simplicity of the device both in construction and operation will be apparent. It shows best by the fact that the movement of a unidirected control disk produces a two-staged control which either runs consecutively through within a single rotation of the cylinder, or in which a time interval can be imposed between the two stages which, according to requirements, may last as many cylinder revolutions as desired, or in which after the completion of the first tripping stage and any desired cylinder revolutions the blacket cylinder may be tripped off again.

A practical embodiment is diagrammatically illustrated in the accompanying drawings by way of example. In these drawings,

Fig. l is an end view of the cylinders of an offset printing machine in their out-of-engagement position.

Fig. La illustrates diagrammatically and on an enlarged scale the displacement of the centre point of the turning axis of the blanket cylinder.

Fig. 2 illustrates the tripping device in a plan view of Fig. 1.

Fig. 3 is a view similar to Fig. 1 with the blanket cylinder in contact with the plate cylinder only, and

Fig. 4 is a similar view with all the cylinders in mutual engagement.

' In the example shown 1 denotes the plate cylinder, 2 the impression or printing cylinder, and 3 the blanket or rubber cylinder of an offset printing machine. The blanket cylinder is journaled by means of an eccentric sleeve or bushing 4 in the side wall 5 of the machine. A shaft 6 is provided to which is fastened a control disk in the shape of a cam 7 having a cam groove 8. This cam is drive from the printing machine so as to make one complete revolution for every revolution of the cylinder and to thereby cause the follower 9 of an abutment plate 10 to perform an oscillatory movement about its pivot bolt 11. Journaled on this pivot bolt is, apart from the abutment carrier 10, a plate 12 which is herein referred to as pawl carrier and which is movably connected at its free end by means of a link 13 to the gland of the eccentric bushing 4 of the blanket cylinder 3. Near its fast end it is provided with a bolt 14 on which is pivoted a pawl 15 with two bearing faces at its ends.

If in accordance with Fig. 1 the lower bearing face of pawl 15 is placed into engagement withthe abutment surface 16 of the abutment carrier 10 with the cam 7 turned in the direction of the arrow from the position of Fig. 3 or 4 into that of Fig. l, the pawl carrier 12 is caused to pivot in clockwise direction so that the abutment 16 pushes the pawl 15 and, therewith, the pawl carrier 12 and the eccentric bushing 4 of the blanket cylinder in a counter-clockwise direction until the blanket cylinder takes the position opposite the plate cylinder 1 and the impression cylinder 2 as indicated in Fig. 1. On the continued rotation of cam 7 the abutment carrier 10 pivots in counterclockwise direction. This movement, however, remains without influence on the tripping members Hand 13, since the upper portion of pawl 15 is positioned outside the reach of the abutments 17 and 18.

If the blanket cylinder 3 is to be tripped to the plate cylinder 1, pawl 15 is brought to engagement, by means not shown, with the abutment 18 of the abutment carrier 10 as shown in Fig. 3. In this position of the abutment carrier the continued rotation of cam 7 moves the carrier 10 from its position in Fig. 1 in counter-clockwise .Fig. 3.

with the plate cylinder 1 on account of the eccentricity of the bushing 4 of the blanket cylinder.

it isdesired to disengage the blanket cylinder 3 from 4 the plate cylinder out of the position of Fig. 3, the lower end face of pawl 15 is moved into contact with the abutment 16 on the abutment carrier 10, so that at the end of the oscillatory movement of this carrier the follower 9 again rests in the flat branch of the cam groove 8, whereby the position of the tripping members 12 and 13 and that of the blanketcylinder as shown in Fig; 1 is reestablished.

In Fig. 4 all cylinders 1, 2 and 3 are shown in their tripped position, whereby the upper end of pawl 15 is in contact with the abutment 17 of the abutment carrier 10. In this case the blanket cylinder 3 has been tripped in substantially known manner in two stages from the position of Fig. 1 first to the plate cylinder 1, as has just been described, and then to the impression cylinder 2.

The positioning of pawl 15 to act in the one or the other sense may be effected in substantially known manner by a manual control comprising a lever 102 which is pivoted on a bolt 101 in the side wall 5 of the machine. The said lever 102'is provided with a handle by means of which it may be turned into the three characteristic positions 103, 203 and 303. Through a tube 104 at the free end of the lever 102 is passed a control rod 105 which is attached to one arm of the pawl 15 by a pin 106. Fitted to the other end of the rod 105 are two preferably adjustable collars 107 and two springs 108, one beingarranged between the tube 104 and the collar 107 at the outer end of the rod 105, and the other between the sleeve or tube 104 and the collar 107 on the inwardly directed part of the rod. Fig. 1 shows the position of the tripping device in its out of engagement position inwhich the control lever 102 takes the position 103 shown in full lines, the lower surface of the pawl 15 thereby resting on the abutment 16.

Shifting the lever 102 into its means position 203 as indicated by the handle being shown in full lines in Fig. 3, pawl 15 moves into contact with the abutment 18 and thereby trips the blanket cylinder 3 to the plate cylinder 1. Further movement of lever 102 into the position 303, as indicated in Fig. 4, causes pawl 15 to move into contact with abutment 17 causing, thereby, the additional tripping of the blanket cylinder 3 to the impression cylinder 2.

The displacement of the turning axis of the eccentric bearing 4 of the blanket cylinder 3 is shown in greater details in Fig. 1a, of which. the now following description must be read in conjunction with the showing of the respective parts in Fig. 1.

The turning axis of the eccentric bearing 4 in the side wall 5 of the machine is denoted by the letter D and the eccentric axis of the bore by 2. It shows that with this arrangement the axis of the blanket cylinder is able to describe an arc from point A to point C passing, thereby, over point B. The connecting line from D to the axis of the plate cylinder 1 is denominated P and to the impression cylinder 1. In the out of engagement position of the cylinders the axis of the blanket cylinder has its position in A, and the distance between the axes of the blanket cylinder and the plate cylinder takes the value P1. If now in the first stage of tripping the blanket cylinder is tripped to the plate cylinder, the axis 2 moves to the point B, thereby reducing the distance between these cylinders to the value P2 with the surfaces of the two cylinders touching each other as shown in Fig. 3.

In the position just described the distance between the blanket cylinder and the impression cylinder is equal to I1 in Fig. La, which means that these two'cylinders are not yet in contact with one another. In the second stage of tripping the axis of the blanket cylinder moves from B to C and the distance between the two cylinders takes the value I2, whereby the surfaces of these two cylinders also come into contact.

During the described movement of the axis of the blanket cylinder from B to C practically no alteration takes place in the distance P2. In the position B and C the said distance remains absolutely the same. Tripping off of the blanket cylinder takes place in the reverse way to the one just described by the axis e moving from C to A over B or, in other words, from the position of Fig. 4 over that of Fig. 3 into the out of engagement position of Fig. 1.

What I claim is:

1. In a tripping device for ofiset printing machines having a blanket cylinder, a plate cylinder, an impression cylinder, an eccentric bushing for the said blanket cylinder and means for turning the said eccentric bushing so as to trip the blanket cylinder consecutively first to the plate cylinder and then to the impression cylinder, a unidirectly revoluble cam member for controlling the movement of the said eccentric bushing into its tripping on and oif positions, a pivotally mounted abutment carrier comprising three abutments for the tripping-on position of said blanket cylinder one for tripping the plate cylinder only, one for tripping successively the plate cylinder and the impression cylinder and one for tripping off at least one of the said plate cylinders prior to the tripping on of the impression cylinder and the said impression cylinder, means for imparting movement from the said cam member to the said abutment carrier, a

pawl carrier and a link pivoted thereto and to the said eccentric bushing, and a pivotally mounted pawl on said pawl carrier adapted for contact with either of the said three abutments and to transmit their movements over the said pawl carrier and the said link to the said eccentric bushing.

2. A tripping device for offset printing machines as set forth in claim 1, in which means are provided for contacting the said pawl on the pawl carrier with either of the said three abutments for transmitting the unidirected movement of the cam member to the blanket cylinder to trip the latter either to the plate cylinder only or first to the plate cylinder and consecutively to the impression cylinder in one consecutive movement, or for effecting the tripping off of either position by actuation of the said pawl in the reverse direction.

3. A tripping device for offset printing machines as set forth in claim 1, comprising, a tripping-off abutment on the said abutment carrier in addition to the two tripping-on abutments, and shift means enabling the positioning of said pawl after the tripping-on of the plate cylinder into contact with the said tripping-0E abutment.

4. In a tripping device for ofiset printing machines having a blanket cylinder, a plate cylinder, an impression cylinder, an eccentric bushing for the said blanket cylinder and means for turning the said eccentric bushing so as to trip consecutively first the plate cylinder and then the impression cylinder, a control cam having a cam track for controlling the movement of the said eccentric bushing into its tripping on and 01f position, means for rotating said control cam from the printing machine in always the same direction, an abutment carrier mounted for turning movement on a pivot on the machine stand, a follower on said abutment carrier for transmitting rocking movement from said cam track to said carrier, two abutments on said carrier for controlling the tripping-on position of said eccentric bushing, a third abutment for controlling the tripping-01f position of the same, a transmission member mounted for rocking movement also on said pivot, a link on said transmission member in connection with the said eccentric bushing, and a pivoted pawl on said transmission member for connection to any of the said three abutments of said abutment carrier for tripping the said blanket cylinder arbitrarily either to the said plate cylinder only, or to the said plate cylinder and consecutively to said impression cylinder, or into its tripping-0E position.

5. A tripping device for ofiset printing machines as set forth in claim 1, in which the pivoted abutment carrier comprises two arms, one carrying the trippingon abutments for the consecutive tripping-on of the plate cylinder and the impression cylinder, while the other arm is positioned opposite said first arm and provided with the tripping-01f abutments for tripping-off respectively the impression cylinder and the plate cylinder in succession, and the plate cylinder only prior to the trippingon of the impression cylinder.

References Cited in the file of this patent UNITED STATES PATENTS 1,087,055 Upham Feb. 10, 1914 1,106,403 Pearce et al. Aug. 11, 1914 1,383,945 Henderson July 5, 1921 2,392,391 Kaddeland Jan. 8, 1946 2,578,700 Harrold et al. Dec. 18, 1951 

